The present invention pertains to pharmaceutical injection devices, and, in particular, to a trigger assembly within an automatic injection device.
Patients suffering from a number of different diseases frequently must inject themselves with pharmaceuticals. A variety of devices have been proposed to facilitate these injections. One type of device is an automatic injection device. This type of device typically includes a trigger assembly that when operated by a user causes the device to automatically insert into the user a needle of a syringe that prior to triggering was disposed within the device housing, and then the device automatically injects a dose of medication through that inserted needle.
One shortcoming with some trigger assemblies relates to the large force required to operate them. For example, in some devices the spring force that in essence opposes the trigger operation also is used to directly drive the syringe plunger. With increasing diameter plungers, or in situations where the medication being acted upon by the plunger is more viscous, larger spring forces are required. Trigger assemblies that directly work against the large force springs in a conventional manner therefore may be difficult for some to operate.
Thus, it would be desirable to provide a trigger assembly for an automatic injection device which can overcome one or more of these and other shortcomings of the prior art.